Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$48.44	11.357%	$53.9413	$53.94	$53.95	$53.90
Purchase #2	$143.77	12.313%	$161.4724	$161.47	$161.45	$161.50
Purchase #3	$131.89	8.272%	$142.7999	$142.80	$142.80	$142.80
Purchase #4	$230.69	11.147%	$256.405	$256.41	$256.40	$256.40
Purchase #5	$91.72	5.735%	$96.9801	$96.98	$97.00	$97.00
Purchase #6	$246.74	13.651%	$280.4225	$280.42	$280.40	$280.40
Purchase #7	$218.88	13.710%	$248.8884	$248.89	$248.90	$248.90
7 purchase totals =	$1,112.13		$1,240.9096	$1,240.91	$1,240.90	$1,240.90